1. Technical Field
The present disclosure is directed to electrosurgery and, in particular, to circuitry for controlling arc energy from an electrosurgical generator for ablating, cauterizing, coagulating, cutting and/or sealing body tissue during electrosurgery.
2. Description of the Related Art
Electrosurgical generators do not have the ability to vary the amount of energy contained within an arc to control the amount of tissue vaporized and the amount of current applied to tissue to limit collateral damage to surrounding tissue, e.g., thermal spread. The ultimate amount of arc energy from the electrosurgical generator to the tissue is dependent on patient resistance, power setting and the internal impedance of the electrosurgical generator.
Vaporization of tissue is proportional to the amount of energy in an arc. This energy in combination with the Cathode Fall Voltage, derives the power for vaporization. Thermal spread is dependent on the amount generated within the tissue is dependent on tissue resistive and the arc energy squared. As can be appreciated, by not controlling the thermal spread the depth of ablation is difficult to predict and control. Electrosurgery is thus disadvantageous in applications in which only a fine layer of tissue is to be ablated, or in areas of the body such as the heart or near the spinal cord where resistive heating can result in undesirable collateral damage to critical tissue and/or organs.
U.S. Pat. No. 6,413,256 B1 to Truckai et al. discloses an electrosurgical system where a spark gap is utilized in series with the electrosurgical generator output current to control resistive heating of tissue during electrosurgery. The spark gap limits the arc energy, but is prone to introducing high frequency oscillations that can have an undesirable effect on the tissue, as well as increase the high frequency leakage currents.
Therefore, it is an aspect of the present disclosure to provide a circuit for controlling arc energy from the electrosurgical generator to minimize the amount of tissue vaporized and to also minimize the amount of current applied to tissue to limit thermal spread without introducing high frequency oscillations or other undesirable effects.